This invention relates to a method and apparatus for automatically cutting or smoothening the surface of a wooden plate while feeding it.
FIG. 18 shows a conventional wood planing machine for automatically cutting the surface of a wooden plate while feeding it. This planing machine comprises a horizontal table 2 fixed to a base 1, a rotary planing cylinder 3 provided over the table 2, and a front (with respect to the feed direction of the plate) feed unit 4 and a rear feed unit 5 having vertically arranged rollers into which the plate is inserted. The planing machine further includes a chip breaker 6 provided between the planing cylinder 3 and the front feed unit 4, and a pressure bar 7 disposed between the planing cylinder 3 and the rear feed unit 5.
The planing cylinder 3 carries a plurality of planing blades 8 on its outer circumference. The upper and lower rollers 10, 9 of the front and rear feed units 4, 5 are both motor-driven, and the upper rollers 10 are vertically movable and normally urged toward the stationary lower rollers 9 by air cylinders 11 or springs. Thus, by driving the rollers 9, 10, a wooden plate A can be fed at a constant speed.
The pressure bar 7 and the chip breaker 6 are independently movable vertically, and are biassed downwardly by air cylinders 12 or springs to press the plate A against the table 2.
When a plate A is fed on the table from the front feed unit 4 with the cylinder 3 rotating, the plate passes under the planing cylinder 3 while being pressed against the table 2 by the chip breaker 6. After its surface has been cut by the planing cylinder 3, it is pressed against the table 2 by the pressure bar 7, and fed out by the rear feed unit 5. The surface of the plate is thus cut over the entire length while being fed at a constant speed.
The chip breaker 6 and the pressure bar 7 press the plate A against the table 2 to prevent shaky motion of the plate during planing and insure stable working. In order to prevent interference with the planing cylinder 3 when they are moved vertically, the chip breaker 6 and the pressure bar 7 are spaced by distances C and B, respectively, from the center of the cylinder, as shown in FIG. 18.
Thus, the leading and trailing ends of the plate are not gripped but get free while the tip of the plate is moving through the interval C and while the rear end of the plate is moving through the interval B, respectively. Thus, over-cut portions or depressions a tend to be formed in the plate near its front and rear ends as shown in FIG. 19, especially if the plate has a tendency to cock.
If, in order to prevent the formation of such depressions, the chip breaker 6 and the pressure bar 7 are pressed harder against the plate, a braking force is applied so that greater power will be needed to feed the plate.
An object of this invention is to provide a method and apparatus for planing a wooden plate which can prevent the formation of depressions without increasing the feed resistance and the plate feed power.